1. Field of the Invention
Our invention is a method for measuring and then determining the total fluid flow and/or its leakage past a barrier.
2. Description of the Prior Art
In many prior art fluid flow measuring devices, the total flow is measured directly. An example of this type of "primary" device is the U.S. Pat. No. 2,936,618 to Milam. Other prior art fluid flow measuring devices indirectly determine fluid flow by monitoring the performance of one or more primary fluid flow measuring devices. Examples of this second class of devices can be found in the U.S. Pat. Nos. 3,711,689 to Park, 3,739,159 to Nalley, and 3,831,447 to Nogita et al. Our invention would fall into the direct or "primary" fluid flow measuring group but with some very important distinctions.
With most direct fluid flow measuring devices, the total flow is generally measured and it assumed any unmeasured leakage past the device is negligible. Where some leakage does exist, normally this leakage is considered to be a constant fixed fraction of the total flow. An ammeter with a shunt is such a device. Assuming the shunted fraction is a fixed fraction of the total flow, this allows the device--like an ammeter--to read the total. When the method of our invention is practiced, the total fluid flow is not directly measured. Moreover, an unknown fraction leaks past the device. This unknown fraction can vary from measurement to measurement. What we do is determine the value of this unknown fraction and then compute the total flow. A complete understanding of the invention will follow from the description thereof hereinafter.
The main advantage of this invention is that it is not necessary to construct a test stopping or barrier which is completely leak-free. The procedures set forth in this invention allow one to calculate the leakage of air around the test barrier and then by summing all the airflow passing through or around the test barrier, to calculate the leakage through the permanent barrier under observation.